A method includes providing a semiconductor structure comprising a varactor region and a field effect transistor region. The varactor region includes a body region in a semiconductor material that is doped to have a first conductivity type. A gate-first process is performed by forming a gate stack over the semiconductor structure. The gate stack includes a layer of gate insulation material and a layer of work function adjustment metal positioned over the layer of gate insulation material. The gate stack is patterned to define a first gate structure over the varactor region and a second gate structure over the field effect transistor region. A source region and a drain region are formed in the field effect transistor region adjacent the second gate structure. The source region and the drain region are doped to have a second conductivity type opposite to the first conductivity type.

Aspects generally relate to a P.sup.N junction varactor that can be integrated with high electron mobility transistor (HEMT) in a single device or die. The varactor and HEMT are fabricated with different materials forming various layers of the varactor and HEMT. Using different material stack-up to form the varactor and HEMT allows characteristics of the varactor and HEMT to be varied for improved performance in different operating scenarios. The integrated varactor and HEMT device may be used for RF circuits, such as radio frequency front end (RFFE) devices for use in 5G.

At least one bipolar transistor and at least one variable capacitance diode are jointly produced by a method on a common substrate.

A circuit includes at least one bipolar transistor and at least one variable capacitance diode. The circuit is fabricated using a method whereby the bipolar transistor and variable capacitance diode are jointly produced on a common substrate.

A method for making semiconductor device may include forming a hyper-abrupt junction region on a substrate and including a first semiconductor layer having a first conductivity type, a superlattice layer on the first semiconductor layer, and a second semiconductor layer on the superlattice layer and having a second conductivity type different than the first conductivity type. The first, second, and the superlattice layers may be U-shaped. The method may further include forming a gate dielectric layer on the second semiconductor layer of the hyper-abrupt junction region, forming a gate electrode on the gate dielectric layer, and forming spaced apart source and drain regions adjacent the hyper-abrupt junction region.

A method for making a semiconductor device may include forming a hyper-abrupt junction region on a substrate. The hyper-abrupt junction region may include a first semiconductor layer having a first conductivity type, a superlattice layer on the first semiconductor layer, and a second semiconductor layer on the superlattice layer and having a second conductivity type different than the first conductivity type. The superlattice may include stacked groups of layers, with each group of layers including stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions. The method may further include forming a first contact coupled to the hyper-abrupt junction regions, and forming a second contact coupled to the substrate to define a varactor.

A semiconductor device includes a first varactor diode and a second varactor diode. The second varactor diode is coupled in series with the first varactor diode and vertically disposed over the first varactor diode. By vertically disposing the second varactor diode over the first varactor diode, the space occupied by the pair of varactor diodes can be significantly reduced.

Gate-all-around integrated circuit structures including varactors are described. For example, an integrated circuit structure includes a varactor structure on a semiconductor substrate. The varactor structure includes a plurality of discrete vertical arrangements of horizontal nanowires. A plurality of gate stacks is over and surrounding corresponding ones of the plurality of discrete vertical arrangements of horizontal nanowires. The integrated circuit structure also includes a tap structure adjacent to the varactor structure on the semiconductor substrate. The tap structure includes a plurality of merged vertical arrangements of horizontal nanowires. A plurality of semiconductor structures is over and surrounding corresponding ones of the plurality of merged vertical arrangements of horizontal nanowires.

A semiconductor device may include a substrate and a hyper-abrupt junction region carried by the substrate. The hyper-abrupt junction region may include a first semiconductor layer having a first conductivity type, a superlattice layer on the first semiconductor layer, and a second semiconductor layer on the superlattice layer and having a second conductivity type different than the first conductivity type. The first, second, and the superlattice layers may be U-shaped. The semiconductor device may further include a gate dielectric layer on the second semiconductor layer of the hyper-abrupt junction region, a gate electrode on the gate dielectric layer, and spaced apart source and drain regions adjacent the hyper-abrupt junction region.

A semiconductor device may include a substrate and a hyper-abrupt junction region carried by the substrate. The hyper-abrupt junction region may include a first semiconductor layer having a first conductivity type, a first superlattice layer on the first semiconductor layer, a second semiconductor layer on the first superlattice layer and having a second conductivity type different than the first conductivity type, and a second superlattice layer on the second semiconductor layer. The semiconductor device may further include a first contact coupled to the hyper-abrupt junction regions and a second contact coupled to the substrate to define a varactor. The first and second superlattices may each include stacked groups of layers, with each group of layers including stacked base semiconductor monolayers defining a base semiconductor portion, and at least one non-semiconductor monolayer constrained within a crystal lattice of adjacent base semiconductor portions.